Project 1 aims to identify the brain networks influenced by acupuncture and to explore the interactions among those brain regions in both healthy subjects and in patients with major depressive disorder (MDD). We hypothesize that the limbic system and default mode network (DMN) constitute major pathways of acupuncture action. Our studies on healthy adults have demonstrated that acupuncture is associated with extensive deactivation in a network of limbic-paralimbic-neocortical brain regions closely related to emotion, cognition, autonomic function and sensory processing. We have also discovered that the brain regions that make up the DMN overlap with the limbic-paralimbic-neocortical regions influenced by acupuncture. The renewal of our CERC will allow us to extend our studies on healthy subjects and translate our findings to MDD. MDD is a highly prevalent mood disorder that can be significantly disabling and a burden to economy, and is known to involve dysfunction of the limbic system. Treatment is problematic and recurrences are common. Several clinical studies suggest that acupuncture may be a safe and economical alternative treatment for depression. Our fMRI studies on healthy subjects demonstrate that acupuncture has prominent modulatory effects on the brain regions that are involved in MDD. We will apply fMRI to explore the possible presence of subsystems in the DMN and LPNN (limbic-paralimbic neocortical network) by comparing the central effects of acupuncture with those of cognitive task and tactile stimulation in healthy subjects. We hypothesize that the temporo-spatial characteristics of acupuncture effects on the DMN and LPNN will overlap for different tasks, but that the preferential spatial distribution will differ. We will compare the effects of these external stimuli on the functional and effective connectivity of these networks. Our studies in healthy subjects will pave the way to studies involving patients with MDD, in whom we will examine the DMN and LPNN responses to facial expressions of fear and anger and the influence of acupuncture compared to healthy controls. We will also explore the effects of acupuncture on the functional and effective connectivity of these circuits in MDD, and correlate possible changes in mood and peripheral autonomic functions with the central effects of acupuncture by fMRI. By demonstrating scientific evidence of acupuncture's beneficial effects on intrinsic regulatory brain organization, the investigation will help to promote the integration of this ancient treatment into modern medical practice.